Electrical discharge device



Dec. 12, 1961 J. J. LOGAN ELECTRICAL DISCHARGE DEVICE Filed Jan. 2, 1958 INVENTOR.

JMES \Y LOGAN ATTORNEYS United States Patent O 3,013,174 ELECTRICAL DISCHARGE DEVICE James J. Logan, Unadlla, NY., assignor to The Bendix Corporation, a corporation of Delaware Filed lan. 2, 1958, Ser. No. 706,715 19 Claims. (Cl. 313-445) This invention relates to electrical apparatus and to a method of making same. In certain aspects thereof the invention relates to a structure including a gas impermeable seal between a metal, electrically conducting member and a ceramic electrically insulating member, and to a method of making such seal.

The invention has among its objects the provision of a novel, improved electrical apparatus having gas sealed parts.

A further object of the invention resides in the provision of an improved electrical apparatus having a gas irnpermeable seal between a metal and a ceramic member.

Yet another object of the invention resides in the provision of an improved electrical apparatus wherein a novel gas impermeable electrically insulating seal is provided between a metal electrically conducting member and a ceramic electrically insulating member.

Yet another object of the invention resides in the provision of an improved electrical apparatus wherein one gas impermeable seal performs the function of sealing and bonding an inner metal member to an outer metal member and an interposed ceramic electrically insulating member.

Still another object of the invention is the provision of a novel method of making a seal between a metal member and a protective ceramic electrically insulating member.

Still another object is to provide an electrical apparatus of the type indicated of such construction that its parts are simplified, production thereof is speeded, and its cost is reduced.

A further object is to provide an improved electrical scription when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention. l

In the drawings, wherein like reference characters refer to like parts throughout the several views,

FIG. l is a view in elevation of an electrical spark discharge device made in accordance with the invention, a portion of the wire leading theretobeing'broken away;

FIG. 2 is a View in Ylongitudinal axial section through the illustrative spark discharge device of FIG. l;

FIG. 3 is a somewhat schematic view in elevation illustrating the method of making the seal in the electrical discharge device of FIGS. 1 and 2, the portion of the discharge device at the location of the seal being shown in axial section, the parts being shown in their preliminarily assembled relationship; and

FIG. 4 is a fragmentary view in axial section through the completed seal in the electrical discharge device.

The invention is illustrated herein in connection with an electrical discharge device which is useful, .for example, as a component of a system fory supplying the starting spark for a jet or ram-jet engine. It will be appreciated that the invention may be used to advantage in a vlarge number of different applications wherein seals are 3,013,174 Patented Dec. 12, 1961 required between parts, particularly gas impermeable high temperature resistant seals between parts of which at least one may be a metal and at least one other part contiguous to the metal part may be made of a ceramic material.

The illustrative spark discharge device is designated as a whole by the reference character 10. Such device, which is of generally circular cylindrical shape, has an outer metal sleeve or sheath 11. The device provides an annular spark discharge gap 12 at its inner end, the gap being formed between a central inner electrically conducting electrode 14, located within the sleeve 11 and insulated therefrom, and an inwardly projecting annular flange 22 on the sleeve. The central electrode 14 is maintained in central axial position within the sleeve by a rst or lower ceramic sleeve member 15 and a second or upper ceramic sleeve member 16, members 15 and 16 snugly tting within sleeve 11. Insulator 16 is of such length as to extend some distance above the upper end of sleeve 11. Electrode 14 is supplied with low tension, gap-energizing electrical current by a wire 17 adapted to be connected to a suitable current source, not shown.

The annular spark gap 12 is located within the lower end 19 of sleeve 11, which functions as a protective hood therefor. Hood 19 is provided with a plurality of angularly spaced holes 20 therethrough, to aid in the propagation of the flame from the gap. The lower end of sleeve 11 is slotted at 2.1, whereby the device 10 may be screwed into a threaded opening well in the housing of an engine or the like. The outer or upper end of sleeve 11 is threaded at 39 to engage the threads on the wall of the opening in the engine housing.

The flange 22 on sleeve 11 has a frusto-conical upper surface. The lower end of the ceramic insulator 15, which rests thereon, has the radially outer portion 25 thereof similarly shaped. Radially inwardly of the lower end of portion 25 the insulator 25 has a fiat lower annular surface 23 which underlies an electrically semi-conductive coating which is interposed between the inner and outer electrodes. Surface 25 is preferably rendered conductive by being platinized, .to improve the electrical contact between ,the outer electrode and the gap-shunting coating on surface 23. A suitable way in which the shunted gap and its outer contact may be made is first to coat surface 23, the surface 25, and the surface of bore 27 of insulator '15 with a suitable electrically semi-conductive material and treating the thus coated insulator to bond the coating thereto.` A suitable coating material for this purpose consists essentially of a mixture of a major amount of cuprousk oxide and anV appreciable but smaller amount of iron oxide in a suitable vehicle. Such coating is applied to the insulator 15 in the locations described, and the insulator is then fired'to drive off the vehicle and bond the solid mixture to the insulator. A suitable semi-conductive coating material is disclosed in the application of Harris, Serial No. 600,210, filed July 26, 1956, now Patent No. 2,953,704.

The described conductive coating is now applied to surface 25 of insulator 15, where it overlies the portion of the semi-conductive coating material on such surface 25. The conductive coating may be applied by painting surface. 25 with a material such as Hanovia #232 liquid platinum.

The lower portion Z7 of the central passage in the lower 'ceramic member 15 snugly receives the central electrode rod 14. The upper portion 29 of the central passage in vmember 15 is of somewhat larger diameter than electrode passage in member 15. The confronting upper end of member and lower end of member 16 are formed to intert and to provide a pocket therebetween for the reception of seal-forming material. In the embodiment shown, such pocket communicates with the electrode 14 and the sleeve 11, whereby an integral seal is formed between members 11, 14, 15, and 16.

The upper end of member 15 has an upstanding annular outer flange 31, such flange providing an annular recess 32 between its inner wall and electrode 14. The lower end of member 16 has a depending inner boss or hub 34 thereon, boss 34 having an outer surface 35 with a diameter somewhat less than the inner diameter of flange 31 and a height generally the same as that of flange 31. When the upper and lower ends of members 15 and 16 interft as shown in FIGS. 2 and 4 the pocket presented between them has outer and inner annular portions lying in planes transverse to the axis of sleeve 11, such outer and inner annular portions being displaced from each other longitudinally of the sleeve 11. The outer and inner portions of the pocket are joined by an interposed elongated annular space coaxial of the sleeve and connected at its outer or upper end to the inner edge of the outer annular space and at its lower or inner end to the outer edge of the inner annular space. The thus formed pocket communicates with both the electrode 14 and the sleeve 11, and thus a sealing material 37 placed in the pocket, and sealed to the parts in the manner to be described, seals all the parts against the passage of gas outwardly from the discharge gap.

The pocket shown, wherein the parts thereof are angularly disposed with respect to each other, forms a more effective seal, and permits a strong bond between the ceramic members 15 and 16. To improve the bond between electrode 14 and sealing material 37, the surface of electrode 14 at the zone of the seal is preferably roughened as by being knul-led, as shown at 36.

The sealing material 37, in accordance with a preferred embodiment of the invention, is made of glass, and is placed in the pocket between ceramic members 15 and 16 in comminuted form. The device is then heated in the vicinity of the seal to heat the glass particles to bonding temperature, ceramic members 15 and 16 being thrust toward each other to compact the sealing glass and to bond the parts together at the seal. A typical procedure in forming such seal will now be described in connection with FIG. 3.

After the lower end of ceramic member 15 has been suitably coated, as described, and preferably while the platinized coating on surface is still wet, so that such coating flows into intimate contact with the outer electrode-forming flange 22, member 15 is assembled into the plug shell or sleeve 11 along with the center electrode 14, the lower or inner end of the center electrode being positioned even with the lower surface of ange 22 on the shell. The sleeve 11 is held upright, as on a lower platen 54, and a predetermined weight of sealing material in comminuted form, as shown at 49, is poured into the upper end of sleeve 11 on top of the assembled insulator 15. Such sealing material is preferably in the form of a glass frit. The upper ceramic insulator 16 is now assembled on top of sealing material 49, as shown in FIG. 3. Following this, an upper platen 55 is placed upon the upper end of insulator 16, as shown. Platen 55 has a hole 57 therein which loosely receives the upper end of center electrode 14 therethrough, the lower surface of the platen around hole 57 resting upon the upper end of insulator 16.

In assembling a typical discharge device 10, a load of from to 40 pounds, including the weight of platen 55, is placed upon insulator 16. The sleeve 16 is then heated in the vicinity of the seal, as by being heated with a gas flame from burner 56. Such heating is continued until the insulator 16 moves downward from the position of 4 FIG. 3 to that of FIGS. 2 and 4. The heating of sleeve 11 is continued for at least 15 seconds after the insulator 16 stops moving downwardly. Thereafter the heating of the sleeve is discontinued, and the sleeve is cooled slowly without forced air blasts.

The described heating and pressing of sealing material 49 causes it to become compacted and bonded together into a unitary sealing structure 37. Structure 37 is bonded to the inner surface of sleeve 11, to the confronting surfaces of insulators 15 and 16, and to the center electrode 14. The pressure to which the sealing material is subjected when heated causes it to flow somewhat into the narrow annular spaces between bores 27 and 30 and the inner electrode, thus more securely to bond and seal the electrode 14 to insulators 15 and 16.

After being tested for the gas tightness of the seal, the discharge plug and lead assembly is completed as follows. The lead wire `17 is soldered to the upper end of electrode 14 at 46. insulating tubing 45 is telescoped over wire 17, and an insulating sleeve 44 is molded about the upper end of insulator 16, the upper end of electrode 14, and the lower end of tubing 45. Washer 41, whereby the sleeve 11 is sealed to an engine housing or the like, is assembled upon the sleeve 11 to lie about the reduced diametered portion 42 thereof and upon shoulder 40. A terminal 50 is then crimped onto the outer end of lead wire 17, and a hood member 51 is then attached over the terminal and to the outer end of tube 45.

The platinized conductive coating on surface 25 of insulator 15 makes an excellent electrical connection with the underlying outer edge portion of the semi-conductive coating. Thus contact difculties between the outer elec trode and the gap-shunting semi-conductive coating are overcome. It will be seen that the same assembly operation which serves to compact the sealing material and form the seal between insulators 15 and 16, and between them and shell A11 and electrode 14 also serves to press the platinized conductive coating on surface 25 of insulator 15 into intimate contact with the outer electrode 2.2. The resulting seal maintains firm contact between the electrically conducting coating on surface 25 and the outer electrode. Thus both the device and the method of assembly of the device are characterized by their economy.

Although only one embodiment of the invention has been illustrated in the accompanying drawings and described in the foregoing specification, it is to be expressly understood that various changes, such as in the relative dimensions of the parts, materials used, and the like, as well as the suggested manner of use of the apparatus of the invention, may be made therein without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art.

What is claimed is:

1. Apparatus comprising a metal sleeve, a metal rod disposed within, extending longitudinally of, and spaced radially from the sleeve, means to seal the rod to the sleeve including a unitary fused gas impermeable body of electrically insulating ceramic material interposed between the rod and the sleeve and heat shaped and directly bonded in situ to the rod and the sleeve, and tubular insulators disposed within the sleeve and about the rod on each side of the seal for maintaining the rod spaced from the sleeve.

2. Apparatus as defined in claim l, wherein the tubular insulators comprise two inner tubular members telescoped over the rod and fitting within the sleeve, and said gas impermeable body is interposed between the confronting end surfaces of the tubular members.

3. Apparatus as defined in claim 2, wherein the confronting end surfaces of the tubular members provide a cavity therebetween having walls with an effective length measured between the rod and the sleeve which markedly exceeds the radial distance between the rod and the sleeve, and the gas impermeable body is disposed in said cavity in intimate contact with, and bonded to, the walls of the cavity.

4. Apparatus as defined in claim 3, wherein the tubular members have bores therein receiving the rod therethrough, the ends of the bores immediately adjacent the cavity are of substantially larger diameter than the portion of the rod thereat, and the gas impermeable body has sleeve-like portions integral therewith extending into said portions of the bores and bonded tothe rod portions thereat and to the walls of the bores.

5. Electrical apparatus comprising a metal sleeve, a metal rod axially disposed within the sleeve and extending longitudinally thereof, means to position the rod within the sleeve comprising two tubular ceramic insulating members telescoped over the rod and closely fittingwithin the sleeve, the confronting end of a first one of the tubular members having an annular axially extending projection thereon and the confronting end of the second of the tubular members having an axially extending annular recess generally complementary to and receiving the projection on the one tubular member, the confronting side and end walls of the projection and recess being spaced to provide a cavity therebetween, and a unitary gas impermeable electrically insulating ceramic body disposed in said cavity in intimate contact with, and directly bonded to, the walls of the cavity, the rod, and the inner wall of the sleeve.

6. Electrical apparatus as defined in claim 5, wherein the ceramic body is made of glass.

7. Electrical apparatus as defined in claim 5, wherein the gas impermeable ceramic body is heat shaped and bonded in situ to the rod and the sleeve.

8. Electrical apparatus as defined in claim` 7, wherein the projection and recess are of substantial axial depth and have confronting cylindrical sidewalls, whereby the cavity has walls with an effective length measured between the rod and the sleeve which markedly exceeds the radial distance between the rod and the sleeve.

9. Electrical apparatus as defined in claim 8, wherein the tubular members have bores therein receiving the rod therethrough, the ends of the bores immediately adjacent the cavity are of substantially larger diameter than the portion of the rod thereat, and the gas-impermeable body has sleeve-like portions integral therewith extending into said portions of the bores and bonded to the rod portions thereat and to the walls of the bores.

10. Electrical apparatus as defined in claim 9, wherein said annular axially extending projection on the first tubular member has a radial thickness which is a substantial part of the radial distance between the rod and the sleeve.

1l. Electrical apparatus as defined in claim 9, wherein the portion of the rod in contact with the gas impermeable seal is roughened.

12. Electrical discharge apparatus comprising a sleeve, a central metal electrode disposed within the sleeve, means to seal the electrode to the sleeve including a unitary fused gas impermeable sealing body of ceramic material interposed between the electrode and the sleeve and heat shaped and directly bonded in situ to the electrode and sleeve, said apparatus including a member interposed between the sleeve and the electrode, an inwardly directed element on the sleeve forming a support for the member and an outer electrode confronting the central electrode, and an electrically semi-conductive shunt-forming surface on the member between the inner and outer electrodes, the sealing body retaining the member in firm contact with the member-supporting element on the sleeve.

13. The method of forming a gas impermeable seal between a sleeve and a rod extending within the sleeve, the sleeve having a portion forming an outerelectrode and the rod forming the inner electrode of an electrical discharge device, comprising placing a first plunger-like tubular-forming member within the sleeve and in teleforming members being made of ceramic electricallyy insulating material, heating the charge of comminuted glass and the sleeve and the rod to bonding temperature,

and thrusting the forming members together to form the glass into a solid gas-impermeable sealing body which bonds the froming members together, spans the space between the rod and the sleeve, and is bonded to the rod and` to the sleeve.

14. The method as defined in claim 13 wherein one of the forming members has an electrically semi-conductive surface interposed between the electrodes, and the electrode on the sleeve is in end thrusting relation with said one of the forming members, comprising applying a flowable coating on the portion of the semiconducting surface of the said one forming member prior to assembly thereof in the shell, and pressing said coated surface of the said one forming member against the electrode on the sleeve simultaneously with the forming of the gas impermeable seal.

l5. Apparatus comprising a metal sleeve, a metal rod disposed within, extending longitudinally of, and spaced radially from the sleeve, means to seal the rod to the sleeve including a unitary fused gas impermeable body of electrically insulating ceramic material interposed between the rod and the sleeve and heat shaped and'directly bonded in situ to the rod and the sleeve, and tubular insulators disposed within the sleeve and about the rod on each side of the seal for maintaining the rod spaced from the sleeve, said gas impermeable body being bonded to the surfaces of the tubular insulators which confront said body. I

16. Apparatus comprising a metal sleeve, a metal rod disposed within, extending longitudinally of, and spaced radially from the sleeve, means to seal the rod to the sleeve including a unitary fused gas impermeable body of electrically insulating ceramic material interposed between the rod and the sleeve and heat shaped and directly bonded in situ to the rod and the sleeve, and tubular insulators disposed within the sleeve and about the rod on each side of the seal for maintainingthe rod spaced from the sleeve, said gas impermeable body filling the space between the confronting end sur-faces of the tubular insulators.

17. Apparatus as defined in claim 16, wherein the gas impermeable body is bonded to the confronting end surfaces of the tubular insulators.

18. Apparatus as defined in claim 16, wherein the gas impermeable body has a radially outer sleeve-like portion extending along the inner surface of the sleeve, a radially inner sleeve-like portion extending along the rod, and a generally radially disposed portion extending between the radially inner and outer sleeve-like portions'.

19. Apparatus as defined in claim 18, wherein the gas impermeable body is bonded to the confronting end surfaces of the tubular insulators.

References Cited in the'file of this patent UNITED STATES PATENTS 

